An analysis of the first-arrival times picked on the DSS and wide-angle seismic section recorded in Italy since 1968

We performed an analysis of refraction data recorded in Italy since 1968 in the frame of the numerous deep seismic
sounding and wide-angle reflection/refraction projects. The aims of this study are to construct a parametric
database including the recording geometric information relative to each profile, the phase pickings and the results
of some kinematic analyses performed on the data, and to define a reference 1D velocity model for the Italian
territory from all the available refraction data. As concerns the first goal, for each seismic section we picked
the P-wave first-arrival-times, evaluated the uncertainties of the arrival-times pickings and determined from each
travel time-offset curve the 1D velocity model. The study was performed on 419 seismic sections. Picking was
carried out manually by an algorithm which includes the computation of three picking functions and the picking-
error estimation. For each of the travel time-offset curves a 1D velocity model has been calculated. Actually,
the 1D velocity-depth functions were estimated in three different ways which assume: a constant velocitygradient
model, a varying velocity-gradient model and a layered model. As regards the second objective of this
work, a mean 1D velocity model for the Italian crust was defined and compared with those used for earthquake
hypocentre locations and seismic tomographic studies by different institutions operating in the Italian area, to
assess the significance of the model obtained. This model can be used in future works as input for a next joint
tomographic inversion of active and passive seismic data.